1. Field of the Invention
The present invention relates to a method of producing a metal band of a metal belt wound around V-shaped pulleys of a belt-type continuously variable transmission and a producing apparatus thereof, more specifically to a producing method and a producing apparatus of metal band which is utilized for connecting a large number of metal blocks constituting the metal belt.
2. Description of the Relevant Art
A belt-type continuously variable transmission using a V-belt and a V-shaped pulley comprising two circular conic disks in which a distance between the two disks is variable is relatively simple in structure, and is inexpensive and thus, is widely utilized.
As a V-belt used in such a belt-type continuously variable transmission, a V-belt as described in Kikai Kogaku Binran (Shadan Hojin, Nippon Kikai Gakkai, new edition issued on Apr. 15, 1987) edition B1, Page 180, has been used as a conventional rubber belt. On the other hands, a so-called metal belt in which a large number of metal blocks are connected through a steel belt (metal band) as described in Japanese Patent Application Laid-open No. 2-225840 has been increasingly used instead of the conventional rubber belt in view of improvement of a tensile strength.
In the above stated relevant art, a lamination typed metal band made of a plurality of metal blanks are utilized for constituting a metal belt which connects a large number of metal blocks to constitute the metal belt. However, the production of the conventional laminated typed metal band is complex and the cost thereof is increased.
The present invention has been achieved in view of the above problems in the conventional metal band for the belt-type continuously variable transmission and producing method thereof.
Therefore, it is an object of the invention to provide a method of producing and a producing apparatus of a metal band of a metal belt for a belt-type continuously variable transmission, in which the production is facilitated and the cost is reduced.
It is another object of the invention to provide a method of producing and a producing apparatus of a metal band of a metal belt for a belt-type continuously variable transmission, in which a tolerance range of difference in size of adjacent blank rings constituting the metal band is large, selection of the blank rings at the time of assembling is easy, a large-scale store place is unnecessary, the equipment cost and the number of management steps can be reduced, and a metal belt having a high precision can be obtained.
To achieve the above object, according to an aspect of the present invention, there is provided a method of producing of a metal band of a metal belt for a belt-type continuously variable transmission, comprising the steps of: superposing a predetermined number of blank rings concentrically on one another to constitute a laminated blank rings; fitting the laminated blank rings to an outer periphery of a circle jig made of material having higher thermal expansivity than that of the blank ring; heating the laminated blank rings together with the circle jig; and deforming the laminated blank rings plastically by thermal expansion of the circle jig.
On the other hand, according to another aspect of the present invention, there is provided a producing apparatus of a metal band of a metal belt for a belt-type continuously variable transmission, comprising: a circle jig having an outer periphery to be fitted with a laminated blank rings which are concentrically superposed on one another; and a furnace heating the laminated blank rings together with the circle jig, wherein the circle jig is made of material having higher thermal expansivity than that of the laminated blank rings, thereby deforming the laminated blank rings plastically by thermal expansion of the circle jig.
According to the producing method and the producing apparatus of the metal band of the metal belt for the belt-type continuously variable transmission of the present invention, since the plastic deformation is applied to the laminated blank rings based on a difference in thermal expansivity between the circle jig and each of the blank rings, a diameter of the blank ring is increased in a true-circle manner by stress uniformly loaded from its inner peripheral side, and a clearance between the adjacent inner and outer rings is reduced. With this feature, when the blank rings are superposed in fitted to the circle jig, a tolerance range of difference between the outer periphery length and the inner periphery length of the adjacent inner and outer rings is largely increased as comparing with a conventional range of 11 xcexcm or less (0 to 11 xcexcm), and even if the outer periphery length of the inner ring is slightly longer than the inner periphery length of the outer ring for example, such a difference can be allowed.
Therefore, a range of selection of the blank rings is largely widened, and since the stocking term after the production of the blank rings is extremely shortened, the store place is unnecessary, or it is possible to reduce the store place, and the equipment costs and management cost are reduced. Further, the final size of the metal belt is determined by the size and the processing temperature of the circle jig, the precision of the size of the metal belt is enhanced by constantly keeping the size and the processing temperature of the circle jig.